The present invention relates to input devices and, more particularly, to an input device such as a mouse or a trackball which includes a roller and a pair of buttons that simulate roller rotation in opposite rotational directions.
Some mouse devices and trackballs include a roller for such functions as controlling cursor movement along a third axis, scrolling, or zooming. The roller is operated by a user finger much like a dial on a radio. For instance, U.S. Pat. No. 5,473,344 shows a user operable roller which includes a shaft extending to an optical encoder wheel. U.S. Pat. No. 5,530,455 discloses a roller having a shaft which drives a belt connected to a pulley on a separate encoder.